linux-kernel - [PATCH 12/35] irqchip/gic-v4.1: Don't use the VPE proxy if RVPEID is set

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Message-Id: <20190923182606.32100-13-maz@kernel.org>
Date:   Mon, 23 Sep 2019 19:25:43 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org
Cc:     Eric Auger <eric.auger@...hat.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <Andrew.Murray@....com>
Subject: [PATCH 12/35] irqchip/gic-v4.1: Don't use the VPE proxy if RVPEID is set

The infamous VPE proxy device isn't used with GICv4.1 because:
- we can invalidate any LPI from the DirectLPI MMIO interface
- the ITS and redistributors understand the life cycle of
  the doorbell, so we don't need to enable/disable it all
  the time

So let's escape early from the proxy related functions.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 drivers/irqchip/irq-gic-v3-its.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 8d6deb75b973..a9976bc81d9a 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3065,7 +3065,7 @@ static const struct irq_domain_ops its_domain_ops = {
 /*
  * This is insane.
  *
- * If a GICv4 doesn't implement Direct LPIs (which is extremely
+ * If a GICv4.0 doesn't implement Direct LPIs (which is extremely
  * likely), the only way to perform an invalidate is to use a fake
  * device to issue an INV command, implying that the LPI has first
  * been mapped to some event on that device. Since this is not exactly
@@ -3073,9 +3073,18 @@ static const struct irq_domain_ops its_domain_ops = {
  * only issue an UNMAP if we're short on available slots.
  *
  * Broken by design(tm).
+ *
+ * GICv4.1 actually mandates that we're able to invalidate by writing to a
+ * MMIO register. It doesn't implement the whole of DirectLPI, but that's
+ * good enough. And most of the time, we don't even have to invalidate
+ * anything, so that's actually pretty good!
  */
 static void its_vpe_db_proxy_unmap_locked(struct its_vpe *vpe)
 {
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	/* Already unmapped? */
 	if (vpe->vpe_proxy_event == -1)
 		return;
@@ -3098,6 +3107,10 @@ static void its_vpe_db_proxy_unmap_locked(struct its_vpe *vpe)
 
 static void its_vpe_db_proxy_unmap(struct its_vpe *vpe)
 {
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	if (!gic_rdists->has_direct_lpi) {
 		unsigned long flags;
 
@@ -3109,6 +3122,10 @@ static void its_vpe_db_proxy_unmap(struct its_vpe *vpe)
 
 static void its_vpe_db_proxy_map_locked(struct its_vpe *vpe)
 {
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	/* Already mapped? */
 	if (vpe->vpe_proxy_event != -1)
 		return;
@@ -3131,6 +3148,10 @@ static void its_vpe_db_proxy_move(struct its_vpe *vpe, int from, int to)
 	unsigned long flags;
 	struct its_collection *target_col;
 
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	if (gic_rdists->has_direct_lpi) {
 		void __iomem *rdbase;
 
-- 
2.20.1